i2c adc driver compilation

Following are two good links to get started.

  1. http://elinux.org/Interfacing_with_I2C_Devices
  2. https://github.com/scottellis/overo-mcp23017

Using i2c-tools is a better idea than writing your own driver initially. In angstrom you can get the package with opkg install i2c-tools.
Check if there is an entry in the /dev for i2c-2, which is the one available on expansion connector on the beagleboard.

I think the includes which you have listed are probably from the kernel source directory?

Also, this link http://www.lvr.com/eclipse1.htm is a good example for cross compiling and debugging for angstrom from a linux host.